Transient Expression of Interleukin-21 in the Second Hit of Acute Pancreatitis May Potentiate Immune Paresis in Severe Acute Pancreatitis.

Interleukin-21 (IL-21) is a cytokine associated with tissue inflammation, autoimmune and infectious diseases. Organ dysfunction and death can occur in patients with acute pancreatitis (AP) in two distinct clinical phases. Initially, a systemic inflammatory response syndrome may be followed by systemic sepsis from infected pancreatic necrosis, known as the "second hit." The expression and possible role of IL-21 in AP has not been established. Thirty-six patients with mild, moderate, and severe AP (SAP) were enrolled. Peripheral blood samples of patients were drawn on days 7, 9, 11, and 13. Reverse transcription-polymerase chain reaction and enzyme-linked immunosorbent assay were performed to determine the expression and concentration of IL-21. Interleukin-21 mRNA levels increased significantly at day 9 in severe (P = 0.002) pancreatitis compared with both the mild and control patient groups. At the protein level, IL-21 was elevated in SAP patients compared with those with mild pancreatitis, although this was not significant. Furthermore, day 9 IL-21 was elevated in septic SAP patients and patients with pancreatic necrosis. Interleukin-21 is transiently elevated in SAP compared with the mild/moderate group, and hence IL-21 may contribute to the immune imbalance that occurs in AP.